CENSUS – Aerobic BTEX and MTBE Integrating Results
Integrating CENSUS Results
Monitored Natural Attenuation (MNA):
Depending on site conditions, aerobic biodegradation of BTEX can be an important component of MNA. Evaluating MNA as a corrective action and aerobic biodegradation as a treatment mechanism often depends upon integrating chemical, geochemical, and microbiological data:
Analysis of BTEX concentration trends (e.g. Mann-Kendall Trend Analysis) can be used determine whether the dissolved plume is stable, shrinking or expanding.
Analysis of electron acceptor concentrations (dissolved oxygen, nitrate, ferric iron, and sulfate) or reduction products (ferrous iron, sulfide, and methane) can be used as indirect evidence of microbial activity. For example, consistently lower DO levels in impacted wells compared to non-impacted upgradient wells suggests oxygen consumption. Likewise, consumption of nitrate and sulfate suggest anoxic and anaerobic activity. Production of ferrous iron and methane in impacted wells indicates iron reduction and methanogenesis.
Select representative wells for CENSUS analysis based site chemistry and geochemistry. Try to include at least one upgradient well, monitoring wells near the source area, perimeter of compliance wells, and downgradient wells outside the dissolved plume. CENSUS analysis quantifies the bacteria specifically capable of biodegradation of BTEX compounds and is a strong indicator that aerobic biodegradation is a component of MNA.
CENSUS analysis quantifies the bacteria specifically capable of biodegradation of BTEX compounds. CENSUS-Expression (RT-qPCR) can be used to quantify the activity of aerobic BTEX degraders and document that aerobic biodegradation is a component of MNA.
Enhanced Bioremediation (Biostimulation):
Monitored natural attenuation can be an effective remediation strategy, however, a lack of available DO can hinder BTEX biodegradation and dictate a more aggressive approach to reach site objectives in an acceptable timeframe. CENSUS analysis can be used to evaluate the effectiveness of engineered approaches to stimulate aerobic BTEX bioremediation. Simply put, increases in aromatic oxygenase genes in wells undergoing treatment demonstrates growth of bacteria capable of BTEX biodegradation.
CENSUS-Expression can also be used to quantify and monitor the activity of aerobic BTEX degraders during treatment.